Hi,
I actually did figure out the issue. It comes down to the XFX cards that Best Buy carries being just terrible. I don't know if they're bottom of the barrel binned or what, but each card I tried that blacked out in the 70's of degrees (often low 70's). I found that by underclocking the GPU and increasing fan speeds, I could keep it under 70 and the issues stopped. I returned these cards, as underclocking a card to keep it alive isn't a good solution.
I switched to a Powercolor Red Dragon that I saw on Newegg and the issues are completely gone. It also runs much cooler and is just as quiet.
